1. Field of the Invention
The present invention relates to an image reading device which, while a film on which a plurality of frame images are recorded is conveyed, reads light transmitted through or light reflected by the frame images so as to obtain image data.
2. Description of the Related Art
A technique for forming an image onto a recording material as follows has come to be known in recent years. A frame image recorded on a photographic film is photoelectrically read by a reading sensor such as a CCD. Image processings such as compression and decompression or various types of correction are carried out on the digital image data obtained by reading. An image is recorded onto a recording material by using laser light modulated in accordance with the digital image data which has been subjected to image processing.
In this technique of digitally reading a frame image by a reading sensor such as a CCD, in order to accurately read the image, the frame image is subjected to a preliminary reading (known as prescanning), reading conditions (e.g., the amount of light to be illuminated onto the frame image or the charge accumulating time of the CCD or the like) corresponding to the density and the like of the frame image are determined, and the frame image is then read at the determined reading conditions (which is known as fine scanning).
A halogen lamp, which is often conventionally used for printing exposure and the like, is used as the light source in the above-described image reading system. However, halogen lamps generate a large amount of heat, and as a result, the efficiency of light-emission is poor and an increase in the reading speed is limited.
Namely, halogen lamps are optimal for use as light sources for cases such as printing exposure in which light is transmitted through a negative film and an image is directly printed onto a photographic printing paper. However, in a case such as the above-described system in which an image is read by a CCD (usually, a linear CCD to which filters are mounted so that each of the three primary colors can be sensed), because the color temperature is low, the amount of light of shorter wavelengths (in terms of color, the B (blue) system) is low, and the SN ratio of the read image is poor (in terms of color, there is too much red). For this reason as well, the use of halogen lamps presents problems to the realization of high speed reading.
When a lamp having a high color temperature (e.g., a xenon lamp or a metal halide lamp) is used as the light source, electrical discharge noise is generated, such that high quality reading cannot be carried out.
Thus, use of LEDs as the light source has been proposed. Because LEDs usually emit light of specific colors (blue, green and red), when the LEDs are disposed so as to be grouped together in close proximity to one another, a white light source is formed. Because LEDs generate little heat and the color temperature thereof is high, they are suited for use as the light source of an image reading system.
At the linear CCD used for reading, a color filter is mounted for each line, and each line detects the density (amount of light) of a color.
However, because the aforementioned conventional structure uses LEDs whose light amounts are lower than that of a halogen lamp, the light must be efficiently supplied to the linear CCD. However, a structure in which all of the emitted light is utilized effectively has not yet been realized.
Thus, there are limits to increasing the conveying speed of the film. High speed reading of images is constrained, which leads to a deterioration in work efficiency.
In view of the aforementioned, an object of the present invention is to provide an image reading device in which there is little heat generated by the light source at the time the light source emits light, images can be read efficiently and quickly and with good image quality, and the device can be made compact.
A first aspect of the invention is an image reading device which, while a film on which an image is recorded is being conveyed, reads the image per predetermined color wavelength, comprising: plural light-emitting element groups in each of which a plurality of light-emitting elements, which emit light at substantially the same wavelength, are aligned linearly along a transverse direction of the film; deflecting means for deflecting optical axes of plural illuminated lights, which have respectively different wavelengths and are emitted from the plural light-emitting element groups, such that the optical axes coincide with one another; a focusing optical system which focuses, in a vicinity of the film, the plural illuminated lights which have passed through the deflecting means; and photoelectric converting elements which receive light which has passed through the film or has been reflected by the film, and subject the light to photoelectric conversion.
In accordance with the first aspect, light-emitting elements of substantially the same wavelength are grouped together and aligned linearly along the transverse direction of the film. Therefore, because all of the light-emitting elements which emit light of a color of a given wavelength can be arranged close together along the transverse direction of the film, a sufficient amount of light can be obtained.
The optical axes of the plural illuminated lights from the plural light-emitting element groups, which illuminated lights have respectively different wavelengths, are made to coincide with one another by the deflecting means. Thereafter, the plural illuminated lights are focused in a vicinity of the film surface by the focusing optical system. The lights of the respective wavelengths which have passed through or been reflected by the film surface are received separately by the photoelectric converting elements.
In this way, the necessary amount of light can be obtained at the photoelectric converting elements, and there are no drawbacks which hinder high speed reading of images.
Because the light emitting elements themselves are small, the overall device can be made more compact than a case in which a halogen lamp or the like is used.
In a second aspect of the present invention, the first aspect further comprises reshaping means for reshaping the illuminated lights, which are emitted from the light emitting elements of the plural light-emitting element groups, into light which is parallel or convergent light.
In the second aspect, when light is focused by the focusing optical system, the light emitted from the light emitting elements is reshaped into, for example, parallel light (or condensed light), so that the light can be used more efficiently.
In a third aspect of the present invention, the first aspect further comprises diffusing means, disposed at a position at which light is focused by the focusing optical system, for diffusing focused light.
In accordance with the third aspect, the diffusing means is disposed at a position at which light is focused by the focusing optical system. As a result, the lights of all of the wavelengths are illuminated onto the surface of the film in a state of being combined together uniformly. Therefore, the color components of the film image can be read accurately by the photoelectric converting elements which correspond to the respective colors.
In a fourth aspect of the present invention, in the third aspect, a degree of diffusion of the diffusing means in a transverse direction of the film is greater than a degree of diffusion of the diffusing means in a conveying direction of the film.
In accordance with the fourth aspect, due to the light being diffused by the diffusing means in the transverse direction of the film, a decrease in the amount of light received by the photoelectric converting elements can be suppressed. However, because it is difficult in actuality to diffuse light in only one direction (the film transverse direction), the diffusing means is designed such that the degree of diffusion thereof in the transverse direction of the film is greater than the degree of diffusion thereof in the conveying direction of the film. In this way, the loss of light can be kept to a minimum.
In a fifth aspect of the present invention, in the first aspect, a direction in which peaks of intensities of lights of respective wavelengths focused by the focusing optical system are aligned, and a direction in which the photoelectric converting elements which receive light of respective wavelengths are aligned, correspond to one another.
In accordance with the fifth aspect of the invention, there is no need to illuminate the light of the plural light-emitting groups uniformly onto the light receiving surfaces of the photoelectric converting elements. For example, if the direction in which the light receiving surfaces which receive the RGB lights are arranged is made to correspond to the direction in which the RGB lights are arranged, it can be ensured that a sufficient amount of light of each color will be received at the photoelectric converting elements.
If the respective colors are completely separated and reach the light receiving surfaces of the photoelectric converting elements corresponding thereto, light of each color can be received even if the photoelectric converting elements are monochrome-type elements.